Signaling system



Au@ 5 94?- B. M. HARRxsoN 2,424,93

SIGNALING SYSTEM Filed Feb. 27, 1943 5 Sheets-Sheet 1 1 TO RECEIVER Z5 yom@ /Q Z,

Iian

ug- 5 1947 B. M. HARmsoN 24,93

l SIGNLING SYSTEM I Filed Feb. 27,: 1943 5 s heetgsheet 5 FIG 7 INVENToRV Ber-ham Harrnson BY ATTORNEY B. M. HAR'RlsoN SIGNALING SYSTEM FiledFeb. 27, 194:" 5 sheets-sheet 4 Fm. lo

mms/T011 BEQTRAM M. HARRISON ug- 5, 394? s. M. HARRxs'oN 2,424,91

SIGNALNG SYSTEM i y File@ Feb. 27, 1941? 5 SheetS-Sheel; 5 00 /2/ oo#F Ny lA 600i W BSW; l I l 400i M9 l m7 I 4 *i zool #l I 15o e s :oo f# g fI .Y

5o g Il l 31.5 I E f Z4 j 1o I, il e l l i. 4 i l l I ll rl I a; 2 4 uIl' i n 0L IN1/M1012. BERTRAM M. HARRISON FISH .BY

Patented Aug. 5, 1947 'l UNITED 1STATES sIGNALING SYSTEM Bertram M.Harrison, l/Yellesley Hills, Mass., as-

signer, by mesne assignments', to Submarine Signal Company, Boston,Mass., a corporation of Delaware Application February 27, 1943, SerialNo. 477,477

9 Claims. (Cl. 161-15) The vpresent invention relates to apparatus fordistance measurement by the use of the time-oftravel method by measuringthe time interval it takes for the energy sent out from a given point toreach the object and bereilected to a point at which the receivingapparatus is located. The present invention more particularly isconcerned with an indicator for `such apparatus by which accuratemeasurements may be made with .the use of equipment 'which iscomparatively simple to construct and reliable in its operation.

In apparatus for distance ranging and depth measurement it is extremelyuseful to have accurate measurements wherever possible. In sound rangingequipment it is extremely useful tc Yprovide accuracy over the entireoperating range While in depth sounding equipment accuracy is desiredmore particularly for shallow depths. It has been the practice in theprior art to use both long-range and short-range scales which usuallyare controlled and operated through a plurality of indicators operatingat different speeds. One of the purposes of the present invention is toprovide both long-range and` short-range scales operating without anychange or shift in the mechanism of the indicator and without the use ofa plurality of indicators or a dual system.

Other features and .advantages of the present invention will be morereadily understood from the specification below taken in connection withthe drawings showing an embodiment of the invention in which Fig. 1 isan elevation partly in section illustrating the invention;

Fig. 2 is an elevation showing a small fragmentary section viewed fromthe left of Fig. 1;

Fig. 3V is a section taken on the line 3-3 of Fig. 1;

Fig. 4 shows a detail with fragmentary sections applied to elements ofFig. 1;

Fig. 5 shows an element of Fig. 4 with curves representing transparentwindows which curves are obtained from the layout of Fig. 6;

Fig. 6 shows a development of the surface of Fig. 5;

Fig. 7 shows a a detail of the element of Fig. 4 withcurves representingtransparent Windows which curves are obtained from the layout of Fig. 8;

8 shows development of the surface of Fig. '7;

Fig. 9 shows a modification in fragmentary Section of a portion of thearrangement shown in Fig. 1;

Fig. 10 shows a modification of afurtler development similar to thatshown in Figs. 6 and 8 combined; and

Fig. 11 shows a further modification of a development somewhat differentfrom thatk indicated in Fig. 10.

The present invention in general employs two concentric cylinders I and`2 which are opaque except for a visible slit on each cylinder whichspirals from one end of the cylinder to the other in a fashion as willbe described later in the specification. These cylinders are rotated inopposite directions and the intersections of the spiral form a windowthrough which a light operated b-y the received signal flashes toindicate by the position of the window at the moment of therash theinterval or distance being measured. In accordance with this generaloutline as described, the presentapparatus is provided with an'nnerlcylinder I and an outer cylinder 2. These cylinders may be made ofglass, Lucite or other suitable transparent material and are providedwith g opaque coatings 3 and 4 except for the spiral slits runningaround the cylinders. The cylinder I may be mounted on a base member 5against a shoulder 6 at the edge ofthe base member. Projecting from thebase member 5 at the bottom is a shaft 1 which is pinned by the pin 8 ina sleeve 9 which is free to be rotated by the gear Il). A supportingbracket II attached to the wall I2 of the casing has a thrust bearing I3on which the shaft 'I and sleeve 9 and the gear I9 may be rotated abouta vertical axis as viewed in Fig. 1. The cylinder I at the top issupported in a shoulder I5 of a flange plate I4 which has a ball-bearingring I6 concentrically positioned with respect to the cylinder I andprovides a bearing for the cylinder with respect to the sleeve or hollowshaft I1. The outer cylinder 2 is similarly provided with an end flange23 and a ball bearing ring I8 permitting free rotation of cylinder 2'.The bearing shaft Il is inserted through a collar 20 which is supportedby' the bracket 2I attached to the wall I2 of the casing by means of thescrews 22 or in some other suitable manner. The cylinder 2 at its lowerend rests in a shoulder 2d of the ilange plate 25 which has an axialcylindrical hole supporting a ball bearing ring 26, which ball-bearingring at its inner side rests against the sleeve 9.

The supporting bracket II and the support I3 furnish a vertical thrustbearing for ythe outer l cylinder 2 and its ilange plate 25 since theballbearing ring 26 rests upon a shoulder of the sleeve 9 and itselfsupports the flange 25 by means of the inner shoulder 21 at the edge ofthe axial opening in the iiange 25. The flange 2'5 is provided with aring gear member 28 by which rthe cylinder 2 is driven. The cylinder Iis driven by the gear II] which meshes with the gear 29 which is drivenby the motor 30 supported by the wall I2. The gear 29 also drives,through the gears 3l and 32 carried on the same vertical shaft 33supported in the bracket Il and rotating in the ball-bearing rings 34and 35, the gear 28 in a direction opposite to that from the gear I0. Itwill also be noted that the cylinder 2 in this arrangement is driven at-a slower speed than the cylinder I, the gear ratio being such to givethe desired difference in speeds, as will be further explained in thespecification below.

Mounted to rotate with the gear 32 is a bracket 36 attached to the gearface by means of the screws 31. This bracket 36 supports a shaft 38which is firmly pinned to the bracket so that this shaft rotates withit. The shaft 38 -is provided with two Ygear wheels 39 and 40. The gear39 meshes with a second larger gear 4I which drives through the shaft42, a switch cam 43 Vclosing once every revolution a pair of contacts`44 in the transmitting or keying circuit.

The gear 40 drives a second gear 45 which also carries a cam 46operating once every revolution, a pair of contact switches 41 in thetransmitting `or keying circuit. The two switches 44 and 41 are inseries with the projector line 4B which transmits or controls theinstant of emission of the signal wave. A short circuit contact 49 isprovided across the keying switch 44 so that this-may be cut out, ifdesired, for the purpose ofproviding a vernier scale operation, as willbe more fully described later. It will be noted that the shaft 38operates at the same R. P. M. as the inner cylinder I and also at thesame speed as themotor 3U if a 1:1 gear ratio is maintained between thegears I0, 29 and 3|, respectively. Therefore by maintaining the samegear ratio between the gears 40 and 45 as between the gears v32 and 2B,the cam 46 will be synchronized with the outer cylinder 2. tacts 41 willbe closed once in every revolution of the cylinder 2 at'thesame relativeposition of the cylinder. 'Ihe cam 43, on the other hand, is rotated ata slower velocity than the velocity of the cylinder 2 in such a relationthat the contacts 44 are closed `every nth revolution of the cylinder 2,the .number n being more fully explained below.

In the circuit arrangement of the system a .sounding may be made onceevery revolution Vof the cylinder ,2 by closing the keying switch 49. Inthis case the contact 44 is cut out of the circuit and since the cam 46rotates in synchronism with the cylinder 2, a signal wave will beprojected at the proper position of the cylinder corresponding to theposition of the cam. This :signal Wave, after being reflected from theobject whose distance is to be measured, is picked up 4over the receiverlines 5D 4and made to operate aashing indicator I which may be of theneon tube type and which is positioned at the axis of the cylinder, theindicator showing through the intersection of the spirals as viewedthrough the slit 5.2 in the plate 53. The plate 53 is provided with twoslits, one numbered 52, already mentioned, and the other numbered 54.Since the spirals may intersect in a number of places, the slits arenecessary to eliminate all but the desired points of intersection, `aswill be more fully explained in connection with the other figures. In

In this manner the conthis connection the light showing through one slit52 may give the shallow depth or short distance indications while thelight showing through the slit 54 may provide the deep indications or,if desired, one scale, for instance 52, may be a Vernier scale. Thiswill more fully appear from the discussion and description in connectionwith Figs. 4, 5, 6, 7 and 8.

Considering first Fig. 8, this shows the development of the gutercylinder 2. The dotted lines 60 and 6i are the Idevelopment of a singleturn spiral indicated by the spiral line 62 on the cylinder 2 of Fig.'1. The point P at the right in Fig. 8 corresponds tothe point P at theleft in Fig. 8, since the two side edges meet when the at sheet isformed into a cylinder. In one revolution, therefore, of the cylinder 2the intersection of the straight line from A to A' with the spiral 62 ofFig. '7 will travel longitudinally down the length of the cylinder fromthe top point A to the bottom point A', making one complete cyclebeginning with the .point a and ending with the point a as viewed inFig. 8. Thestraigh-t line A-A .may be Vmade to coincide with .the window slit 52 by means of which the indication would be iixed and visiblewith reference -to the indicating scale.

On the same cylinder 2 there maybe provided asecond spiral curve 63which is shown in development by the lines 64, 85, 66, 61, 68 and 69.This makes five complete wraps about the cylinder. Its end points do notcoincide with those of spiral 62. They are `indicated atB and B' onFig.. '1 and at' b and b" on Fig. 8. .As the cylinder rotates the endsof spiral 63 trail the ends of spiral 62 by .the circumferentialdistance AB', Fig. 7, which corresponds to the distance .separating theslits 52 and `54 in the plate 5,3. The spiral 63 intersects the slit 54in ive points, as can be seen by laying a straight-edge vertically uponFigure 8. However. when cylinders I and 2 .are assembled as shown inFig. 1, and both are driven at the proper .relative speeds, four ofthese in intersections are masked :by the cylinder I, i. e. only one ofthe iive'intersections of spiral 63 with slit 54 is superposed on acooperating spiral 11 on cylinder I at any instant.

The outer cylinder 2 has, Yfor example, Ybeen shown with two spirals B2having one convolution and B3'having ve convolutions which means thatthe ratio of the measuring scale is 1 to 5 with respect to the windowopening 52 .or 54.

The inner cylinder I shown in Fig. 5Y has, Yfor the sake of example,been provided with spirals 10 of 1.2 convolutions and a second spiral 11of 6 convolutions. In the development in Fig. 6 the line 1I correspondsto the spiral 10 of Fig. 5. In addition other similar spirals are shownon the layout identified by lines 13, 14, 15 and 16. Similarlycorresponding to the spiral 11 of Fig. 5 its development is shown inFig. 6 by the lines 18, 19, im, 8|, 82 B3 and 84.

When the cylinders are assembled as indicated in Fig. 1 and .are rotatedin opposite directions, the intersection of the properly associatedspirals will travel along a straight line coinciding with the desiredwindow opening 52 or 54. It will be understood in considering thespirals on windows I and Y2 that only those which are intended tocooperate to form the desired point of intersection need be used.

Consider in the iirst instance the association of the spiral 1.0 oncylinder I with the spiral I62 on cylinder 2. The intersection of thesetwo spirals Will take place in a straight line corresponding to thewindow opening 52. Since, however. the cylinder 2 will make asinglerevolution while the cylinder I will make 1.2 revolutions, becauseof the gearing between cylinders, on the secondrevclution of thecylinder 2 the spiral 10 will have advanced to a position different fromthat of the starting point C. In the additional family of spirals shownin Fig. 6, which is also applied to Fig. 5 (but not shown), the spiralcorresponding to the line 13 will be at the starting point C and onsubsequent revolutions the spirals corresponding to. the lines 14, 15and 16 will each be at the starting point so that, in effect, a completecycle will be made for six revolutions of the cylinder or fiverevolutions of the cylinder 2 with the intersections occurring along theline corresponding to A-A in Fig. 7 which corresponds to the indicatorwindow opening 52 of Fig. 2. This intersection of spirals correspondingto 10 on cylinder I and 62 on cylinder 2 will produce a relatively longlength of scale in compact form which covers ve times the unit scalelength of the Window opening 52.

'I'he second group of spirals, namely the spiral 'I1 of cylinder I and63 of cylinder 2 may be used toproduce an indication which would appearas an intersection traveling down the length of the window 54corresponding to the lines D-D, Fig. 5, and B-B on Fig. 1. Thisintersection will travel downward behind the window opening 54 once inevery five revolutions of the slower cylinder 2 or once in every sixrevolutions of the faster moving cylinder I.

For the proper chosen speed of rotation of cylinder 2 the calibration ofthe scale will be determined depending upon the following formula:

1w Fr@ where F is the number of revolutions of the cylinder per unittime, n equals the number of convolutions of the spiral, 'D equals thevelocity of the propagating wave in the medium and 2d equals the totaldistance of travel of the wave starting with a measuring pointcorresponding to the moment when the indicator was at a zero position.In the case of the measurement of distances or depth where the signal istransmitted from the point where the indicator is located or in itsimmediate vicinity, d equals the distance of the refiecting object.

In the arrangement, therefore, shown in Figs. 5, 6, 7 and 8 the scale atthe right is in eiect five times as large as the scale at the left andif the entire measuring distances Were 5000 feet, then inthe first 1000feet the indicator in the right Window would travel the length of thescale while the indicator in the left Window would travel one-fifth ofthe scale. In the second thousand feet the indicator at the right wouldagain travel the whole scale while that at the left would go between the1000 mark and the 2000 mark.

The keying arrangement should now be quite obvious from the descriptionof the operation of the scale. When shallow distances are to be measuredor rather when a short scale is to be used, a signal for everyrevolution of the cylinder 2 will produce by the combination of thesingle spiral 62 of the cylinder 2 and the family of spirals of cylinderI signal impulses at the beginning of the travel of the indicator downthe scale length.

Referring to Figs. 6 and 8, the rst indication will begin with theintersection of the lines 60 and 1| for the first revolution while forsucceeding revolutions the indications will begin with the intersectionof the line 60 with the lines 13, 14, 'I5 and 16, respectively. In thewindow 54 to the left of the window 52 the intersection of the spirals53 and 11 will be visible and this intersection will begin referring tothe development of Figs. 6 and 8 with the intersection of the lines 64and 18 at the top of the scale at the instant that the key 49 is closed.The intersection of the two spirals at the top of the scale, however,will occur only once in every ve revolutions of the slowest spiral. Forthis purpose the contacts 44 are placed in series with the contacts 4'Iso that the projector circuit may remain open until every fifthrevolution of the slower cylinder 2. Therefore, the operation of thissystem will be as follows, assuming that the system is being operatedfor deep depths.

The key 49 will be left open, the cam 43 will travel at one-fth of therotational velocity of the cam 46 and allow a signal to be produced bythe projector once in every fifth revolution of the cam 43. The cam 46is synchronized with the cylinder 2 and with the cam 43 in such aposition so that both cams 43 and 46 close switches 44 and 41 andproduce a signal at the instant that the spiral curves 63 and 11intersect in front of the scale window 54' which is the zero point ofthe scale. At this saine instant the spiral 10 intersects with thespiral 62 at the zero point of the scale in front of the scale window52. The signal is emitted and after reflection from the object whosedistance is to be measured is received by the receiver over thereceiving line and made to operate the indicator 5|. If this should bewithin the first revolution of the cylinder 2, an indication will showby the intersection of the spirals 10 and 62 somewhere along the window52. A corresponding indication will also show in the rst fifth sectionof the window 54. Ifv the signal returns in the second revolution of thecylinder 2, the intersection will ocur with a spiral corresponding tothat of the line 13 in the development of Fig. 6 and the intersection ofthe spiral I1 and 63 will be in the second fth of the scale 54. In thismanner the scale 52 will be a Vernier scale for the exact indication ofthe larger unit as indicated in the scale 54. The operator will,

. therefore, read the last figures of the depth indicated on the scale52 and the first 'lgures on the scale 54.

A somewhat different arrangement than that described above is indicatedin Fig. 10. Here the full-line diagram shows the development of thecylinder I and the dotted-line diagram 9| shows the development of thecylinder 2. In this figure the family of lines 92, 93, 94, and 96corresponds to the family parallel with the lines 1| of Fig. 6, and thebroken lines 91 correspond to the lines 60 and 6| of Fig. 8. The spiralsform the 'basis for the Vernier scale indications. The coarse scale inthis case, however, is arranged below the Vernier scale and shows in thedevelopment of two spirals the spiral of six turns on the smallercylinder corresponding to the full lines 98, 99, |00, IOI, |02, |03 and|04, and the spiral of ve turns on the larger cylinder corresponding tothe broken lines |05, |06, |01, |08, |09 and ||0. The intersection ofthe spirals, producing with the flashing indicator the desiredindication will therefore travel five times down the top scale whileanother intersection corresponding thereto will travel the length of thelower scale.

Other types of scales may be used according to the particular purpose towhich they may be applied'. In Fig. y1'1 there is shown a logarithmicscale in which the dotted logarithmic curves I I I, H2, H3, H4 and H5belong to. the slower and larger cylinder, having five wraps for a.complete travel of the spiral with respect to the scale. The curvescorresponding to the smaller cylinder will have `logarithmic spiralscorresponding to the lines |16, II'I, H8, IIS, |20 and I2I, making sixwraps on the cylinder for the complete scale. This type of scale becauseof its nature differs from the scales in .the othergures in that thescale is enlarged at the beginning and decreased towards the 'end inaccordance with the exponential function to which vthe scale and spiralcurves are plotted. In this case, however, one complete measuring cyclewill comprise five revolutions of the larger scale and siX revolutionsof the smaller scale with no repetition as in the previousillustrations. On the other hand, the indication will travelcomparatively rapidly during the rst part of the scale graduallydiminishing in velocity to the end of the scale. By this means shorterdistances will be read more accurately where greater accuracy isrequired. The logarithmic curves may be of a simple nature as forinstance Y=ez1. VIn the scale of Figure 1l the point 31.6 is half thescale or V1000.

The invention has'been described in connection with spiral convolutionshaving iive and six revolutions. However, any desired combination may beused and should be chosen in accordance with the velocity oi the signalin the Ypropagating medium, the accuracy of readings required and theapproximate range of Vthe apparatus. present invention is will be notedthat while the cylinders I and 2 rotate at diierent velocities, thevelocity need not be changed from its originally designated value forthe purpose of producing accurate short distance readings and longdistance readings as well.

Further arrangements and combinations of types of scales, spirals andvariations in speeds of the indicating cylinders are readily suggestedby the description set forth in this specification.

In the arrangement of Fig. 9, the same general construction is employedas in Fig. 2 with the eX- ception that the indicator is in the form of abent tube 5I.

Having now described my invention, I claim:

1 In a device for measuring time intervals, an indicating deviceincluding a pair of concentric cylinders, means for rotating the same inopposite directions at diierent speeds having a fixed ratio to oneanother, one of said concentric cylinders having a spiral curving in onedirection and the other of said cylinders rotating at the faster speedhaving a family of spirals curving in the opposite direction with ashorter pitch than the spiral on the rst cylinder, said single spiraland said family of spirals providing in successive revolutions of theslower cylinder single intersections aligned along an axial element ofthe cylinder, said intersections forming Windows permitting illuminationto show through, an illuminating indicator positioned in line with saidVaxial element and means for providing an illumination of said indicatorat the end of the time interval being measured l2. A device formeasuring the time duration l In the of recurrent phenomena comprisingtwo rotatable concentric cylinders having groups of curves spiralling inopposite directions, said curves being chosen in such a manner and saidconcentric cylinders havingv such related speeds that the spirals`intersect upon lines parallel .to vthe axis of the cylinders, one groupof intersections forming an elongated scale and another group .formingan abbreviated scale whereby the first vserves as a Vernier for thesecond, means `for rotating said cylinders in opposite directions, andmeans providing an indication at the end of the time interval beingmeasured for producing an indication of the locus of the intersection ofsaid spirals.

3.111 a system for measuring time intervals the combination of twoconcentric cylinders, one having means forming a translucent spiralcurve spiraling in one directionaround the cylinder in a given `pitchand the other 4having a family of translucent spiral curves spiraling inthe opposite direction in a pitch diierent from the pitch of the `rstspiral, means for rotating said cylinders in opposite directions atvelocities such as to maintain the intersection of said spirals ondifferent cylinders along a chosen line parallel to an element of saidcylinders, and means operatively associated with the rotation of saidcylinders for periodically initiating the beginning of the time intervalto be measured when a point on the spiral of the first-named cylinderintersects a given point on one of the family of spirals on thesecond-mentioned cylinder, means forming a mask Aabout the line ofintersection, and means for indicating momentarily the point ofintersection of said spirals at `the end of each time interval.

4. In a system for measuring time intervals the combination of twoconcentric cylinders, the first having two independent translucentspiral curves spiraling thereabout in the rsame direction at differentpitches, one spiral curve making substantially more convolutions thanthe other spiral curve, the second cylinder havingt a family oftranslucent spiral curves coiled about it all of the same pitch and asecond translucent spiral curve coiled about it in the same directionas, but making substantially more convolutions than the family ofspiraling curves, the ratio of the pitches of the iirst spiraling' curveof the rst cylinder to that of the family of spirals of the secondcylinder being the same as the ratio of the pitches of the secondspiraling curve of the first cylinder to that of the second spiralingcurve of the second cylinder, means for driving said cylinders inopposite directions in angular -velocities corresponding to the ratio ofthe pitches whereby the intersection of corresponding spirals on thecylinders travel along a line parallel to an element of the cylinder,the intersection of the family of spirals on the second cylinder withthe first-mentioned single spiral on the first cylinder providing a longscale measurement and the intersection of the other individual spiralson each cylinder furnishing a short scale measurement whereby twodifferent scale measurements may be obtained Without varying the speedsof the cylinders.

5. In a system of the type described, an indicator comprising twoconcentric cylinders having opaque surfaces with each surface beingprovided with translucent spiraling curves cooperating together toproduce translucent intersections permitting visual indications to begiven, the ratio of pitches of the spirals on one cylinder to thecooperating spirals on the other cylinder being the same, means fordriving said cylinders in opposite directions at angular velocitiescorresponding to said ratios whereby the intersections of thecooperating spirals occur in 9 lines parallel with an element of thecylinder, one of said lines providing the short measurement scale andthe other providing the long measurement scale.

6. In a measuring system of the type described, an indicator comprisingtwo concentric cylinders having opaque surfaces with each surface beingprovided with translucent spiraling curves cooperating together toproduce translucent intersections permitting visual indications to begiven, the ratio of pitches of the spirals on one cylinder to thecooperating spirals on the other cylinder being the same, means fordriving said cylinders in opposite directions at angular velocitiescorresponding to said ratios whereby the intersections of thecooperating spirals occur in a line parallel with an element of thecylinder, one of such lines providing a short measurement scale and theother providing a long measurement scale, and means operativelyassociated with the rotation of said cylinders for initiating thebeginning of a measurement periodically when a point of the cooperatingspirals intersect in a new repeated cycle in said line.

7. A device for measuring the time duration of recurrent phenomenacomprising two rotatable concentric cylinders having logarithmic curvesspiraling in opposite directions thereabout, said curves providing bytheir intersection an indicating element which, upon rotation of saidcylinders in opposite directions at properly related speeds, travelsaxially with respect to said cylinders along a predetermined line, meansfor rotating said cylinders at such properly related speeds, means formasking said cylinders except for said predetermined line, means adaptedto be operated at the termination of the phenomena being timed forproducing an indication of said intersection, and means synchronizedwith the rotation of said cylinders for initiating said phenomena.

8. A device for measuring the time duration of recurrent phenomenacomprising two rotatable concentric cylinders having logarithmic curvesspiralling in opposite directions thereabout, said curves providinggroups of intersections adapted to progress axially with respect to saidcylinders when said cylinders are rotated in opposite directions atproperly related speeds, means for rotating said cylinders in theaforementioned manner and a window provided in a xed position parallelto the axis of the cylinders, said spiralling curves being of suchcharacter and so positioned and said cylinders being rotated at suchspeeds that in successive revolutions of one of said cylinders differentspiral intersections travel along said window, a series of saidintersections constituting, in a number of revolutions of said onecylinder, a complete cycle in which the scale length becomes a functionof the number of revolutions forming said complete cycle.

9, A device for measuring the time duration of recurrent phenomenacomprising two rotatable concentric cylinders, vmeans for rotating saidcylinders in opposite directions, one of said cylinders being providedwith a spiral having a convolution or" a single turn and the other ofsaid cylinders having a family of similar spirals of a convolutioncomprising a turn and a simple fraction thereof, each spiral oi thefamily lagging the next by the same angle, said cylinders also havingeach one other spiral in the same relation of convolutions as that ofthe spiral having a single turn and the -spiral constituting a singleturn and a fraction thereof, means for rotating said cylinders inopposite directions at chosen speeds whereby in successive revolutionssaid rst mentioned spiral of single turns will intersect along the sameline with the family of spirals having a turn and a REFERENCES CETED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,243,343 Johnson May 27, 19412,098,287 Gent 1 Nov. 9, 1937 2,054,109 Williams Sept 15, 1936 1,528,772Kaminski Mar. 10, 1925 729,164 Haskins May 26, 1903

